The Sedalia weekly bazoo. [volume] (Sedalia, Mo.) 187?-1904, 1887-11-22

Details Explaining the Work Of Excavation
and Pressure of Air.

For seven years work has been pro-
crossing upon a tunnel under the Hud-
SON river. between the Hoboken and
Erie ferries, to connect New York and
Jersey City. Want of funds has pre-
vented its completion at the contem-
plated date, but it is constantly in
oreasing its length, and the meeting Of
the sections seventy feet beneath the
surface of the river is sure to be ac-
complished in the not very remote fu-
ture. Two tunnels are in fact being
constructed side by side, one of which
has been extended a distance of
2,100 feet, the other $50 feet.
The daily average of progress
made at a heading is 81 feet
The exterior of the tunnel con-
sists of Hanged plates of boiler
iron bolted together so as to
form a circular tube about "a feet in
diameter. Within this iron tube is q
lining of brick "a feet thick, giving rig
idity and permanence TO the completed
tunnel. The work is advanced at the
heading by adding one by one Hanged
plates to those already bolted in posi-
ton at the forward end. Excavating
the silt that forms the bed of the Hud-
son, placing the plates, building the
brick work, and advancing the interior
tube, called the pilot" all go on at
the same time. The pilot, an iron
tube feet in diameter and so feet
long. is kept about Is feet in advance
of the tunnel itself, and serves some
what the purpose of an outwork for
the advance guard for the gang of
workmen engaged in digging. boiling
on plates, and hauling out the exca-
yated dirt The pilot is advanced by
plates from its rear end and
placing them in front as the work adj
yances. 1t might be supposed that
the pressure of 60 feet of water above
the mouth of the tunnel would cause
mud and water to enter and overwhelm
the workmen. This would no doubt
occur but for the system of locks en-
ployed to confine the air in the end of
the tunnel when work is going on.
Air is forced in, in fact, until a pressure
of 80 pounds to the square inch is gained,
which pressure, experience shows, suf-
fees to balance the pressure of the
river. If the pressure falls below this
figure water begins to trickle through
the silt into the heading; if it is ex-
ceeded the water is driven out, and the
silt losing conference, begins to crumble
and fall down into the heading. Not
little air escapes, in fact, from the
heading, and produces at the surface
of the river, in midstream, peculiar
circular patch of white foam. due to
the raising of a multitude of minute
bubbles. The principle of the pneu-
matte lock is not unlike that of the or
binary canal lock. Two walls are built
across the tunnel with suitable space
between. In these walls are large
doors opening inward. When
the workmen 60 to their work in the
they first pass within the outer
wall, and thereupon the iron door is
shut behind them and air is forced in
until pressure ofS2 pounds per square
inch is obtained. When that pressure
is reached the iron door of the inner
wall is easily opened ard the men pass
within to the heading. The excavated
is hauled out by mules on q
that traverses the lock. Light
is obtained from 16 candle-power in
electric lamps. and also
from candles, which burn fiercely un-
der the increased pressure of the air.
The tunnels are evidently a difficult
and costly undertaking, but in view Of
the great advantage for handling traf-
fic they will give the company who
owns them, it is somewhat surprising
that money was not forthcoming in
abundance to secure their completion
years ago. Toavoid the ferries and be
able to land traffic of all sorts in New
York without delay ought. one would
think, to excite the transportation COM
panies to make the greatest possible eff
forts. Perhaps there are vested inter-
ests that find profit in the existing i'm
perfect arrangements Chicago
Times.
The seashore is vexatious to bar
Ders. The moist air makes il difficult